Polyurethane elastomer gel insulating composition and use thereof

ABSTRACT

The invention relates to the use of a thermally insulating composition in the form of crosslinked polyurethane elastomer gel, obtained by reacting at least one polyol and at least one polyisocyanate in the presence of at least one inert organic filler, for the thermal insulation of pipeline systems present in a product-transfer conduit.

CROSS REFERENCE TO RELATED APPLICATION

This is a national stage application (filed under 35 U. S. C. 371) ofInternational Application PCT/FR01/03339.

The present invention relates to the field of thermal insulation,particularly to thermal insulation of conduits for transport or transferof materials. It describes the use of an insulating composition in theform of a crosslinked polyurethane elastomer obtained by reacting apolyol and a polyisocyanate in the presence of an organic fillerchemically inert to isocyanates, this filler preferably being at leastone thermally insulating liquid.

The present invention finds its application in technical fields whichuse conduits or pipeline systems for transferring, evacuating ortransporting materials which are liquid and relatively viscous, where itis necessary to maintain the temperature of the materials during theirtransport or to limit the heat losses, or to heat the transport conduitsif shutdown occurs. An example which may be cited is the field oftransport of petroleum products from a land-based or submarine well, ofhot-water conduits for district heating, of conduits for heating orcooling industrial lines, the field of air conditioning andinstallations needing the maintenance of high or low temperature, andbuildings insulation.

In these fields there are often problems of heat exchange and ofmaintaining the temperature of the transported products. This is becausepoor insulation can cause a variety of disadvantages. For example,viscous products are transported at relatively high temperature. Poorinsulation combined with a lower-temperature environment brings about alowering of temperature, an increase in the viscosity of the transportedproduct, a slowing of flow rate, which can even result in deposition, orgelling and plugging of the conduit, with serious consequences ifshutdown of production results.

It may also be noted that an increase in the temperature of atransported product can irreparably impair the properties of thisproduct and possibly cause its total degradation, or if volatileproducts are being transported, can create increases in pressure andrisk of damage to the conduits, and explosion risk.

It is therefore necessary to provide thermal insulation for conduitsserving for the transport or the transfer of materials, in particularrelatively viscous liquid materials, by using insulating materials whichare easy to process at the actual point of application, in particulareasy to mould between the walls of the sheath and of the conduit, withgood adhesion and good impermeability of the assembly and with highcompressive strength performance, more particularly under the conditionsof transport through submarine pipes at great depth.

To resolve the abovementioned problems, the applicant's inventionproposes insulating the conduits with the aid of a thermally insulatingpolyurethane gel obtained by reacting at least one polyol with at leastone polyisocyanate, in the presence of at least one organic fillerchemically inert to isocyanates, the said organic filler preferablybeing based on at least one thermally insulating liquid.

This follows from the applicant's finding that insulation with this typeof gel provides a means of:

-   -   obtaining very low λ (lambda: thermal conductivity) with high        compressive strength. This is not the case with elastomers        filled with solid materials, such as hollow glass beads, fibres,        cork, etc. The behaviour of the gel is actually close to that of        an incompressible liquid    -   providing ready capability for modifying modulus of elasticity        or density    -   providing increased ease of processing by methods such as        injection moulding or premoulding    -   manufacturing transfer conduits which are relatively flexible,        thermally insulated, and capable of being rolled up onto reels,        with completely satisfactory adhesion of the moulded insulating        material and assured impermeability of the assembly.

The transport conduit may have various forms, but is preferably tubular,like the sheath around the transport conduit. Both the transport conduitand the outer sheath may be made of metal, such as iron, steel, copper,aluminium, or metallic alloys, but may also be made of syntheticpolymers, such as polypropylene, polyethylene, PVC, polyamides,polyurethanes, or any other polymer convertible into pipes, sheets, orsheathing. The abovementioned option of sheathing made of polymers is anoption rendered more practical and effective by the fact that thesolution of the invention, which permits a gel to be obtained whoseincompressibility performance is equivalent to that of a liquid, permitsthe use of sheathing materials which are less rigid, lighter in weight,and less difficult to process, and which consequently incur lower totalcosts.

The outer sheath may preferably be a thick, relatively rigid layer ofthickness from a few millimetres to some centimetres, but may also takethe form of a flexible or semi-rigid film.

The free space between the transport conduit and the outer sheath, wherethe insulating gel will be applied, may be variable, and itsspecification depends on the desired degree of insulation, calculatedfrom the insulation factor of the gel and from the temperatures to bemaintained.

Other insulating materials may be used in combination with theinsulating gel, by superposing or intercalating various insulationlayers.

It is possible to combine the polyurethane gel with an insulating foam,such as rigid insulating polyurethane foams, syntactic foams, polyolefinfoams, expanded polystyrene or mineral insulating materials, such asglass fibre or rock fibre. These compact or expanded materials may makeup the outer sheath, inside which there is the gel applied onto thistransport conduit. Compared with these standard insulating materials,the minimum and essential advantage of the insulating gel of the presentinvention is compressive strength. All the standard insulating materialshave the disadvantage of crushing under compression unless they have theprotection of a rigid sheath surrounding the insulating material.

Another advantage of the invention is the capability of using thecomposition in liquid form at the actual points of use, or in the formof premoulded crosslinked gel.

For example, before its crosslinking and conversion into gel, the liquidmay be poured or injected between the transport conduit and the outersheath, the crosslinking taking place in situ, but the insulatingmaterial may also be applied in the form of premoulded crosslinked gel,in the form of sheets, of tapes or of mouldings of dimensions defined bythe insulation objective to be achieved.

The advantage of the composition of the invention in the form of gel,other than very good thermal insulation performance, is the ability ofthe gel to fill all the empty spaces and interstices, to adhere tonumerous substrates by exhibiting tack, to deform under stress,distributing pressure, with behaviour equivalent to that of anincompressible liquid. The gels described in the invention have verygood elastic recovery and regain their initial shape once the stressesare removed. Resistance to high pressures and ease of processing in situat the actual point of use are particular advantages for the thermalinsulation of submarine transport conduits.

The elastomeric gels of the invention provide not only insulation butimpermeability to liquids and gases.

The present invention therefore provides the use of a thermal insulationcomposition in the form of an insulating gel for insulating pipelinesystems present in a product-transfer conduit. The insulating gel isobtained from a crosslinkable composition comprising at least onepolyol, at least one polyisocyanate and at least one chemically inertorganic, preferably liquid, filler.

The crosslinkable insulating composition according to the presentinvention therefore comprises at least one polyol, at least onepolyisocyanate of functionality ≧2, optionally a crosslinking catalystand a sufficient quantity of at least one chemically inert organic,preferably liquid, filler.

After crosslinking, the composition according to the present inventionis a low-exudation or zero-exudation homogeneous rubbery solid.

According to the present invention, use is made of an organic fillerchemically inert to polyisocyanates, its weight being greater than 20%by weight, preferably from 50 to 95%, and more preferably from 60 to 90%by weight, of the entirety of the crosslinkable insulating composition.

According to the present invention, the organic filler chemically inertto polyisocyanates is an insulating liquid compatible with polyols andpolyisocyanates. This insulating liquid filler may be chosen amongplasticizers, such as oils, resins and hydrocarbon derivatives,hydrocarbons and fuels, alkylbenzenes and liquid esters.

It is more particularly chosen among:

-   -   1) Amorphous or semicrystalline paraffins (of melting point ≦50°        C.), including animal waxes, vegetable waxes (such as candelilla        or carnauba primarily composed of a mixture of aromatic and        aliphatic esters), mineral paraffins and synthetic paraffins        (polyethylene waxes, chlorinated paraffins, etc.). Those of most        interest for the invention are the “mineral” paraffins:        petroleum derivatives. They consist mainly of n-alkanes. The        paraffins are microcrystalline, brittle and composed of 40–90%        by weight of normal paraffins, the remainder consisting of        C₁₈–C₃₆ cycloalkanes and isoalkanes. They are obtained by        distillation of crude oil. This is generally followed by        decolorizing by hydrogenation or percolation. They are more        preferably chosen among paraffins: C₁₈–C₂₀ n- or isoparaffins        and mixtures thereof or chlorinated paraffins. Typical examples        of paraffins are:    -   n-heptadecane, n-octadecane, n-nonadecane, n-eicosane,        n-heneicosane, n-docosane and mixtures of these paraffins, for        example LINPAR 18–20 from the company CONDEA

2) Naphthenic oils or resins, more particularly the C₅–C₁₂representatives: naphthenic oils are also petroleum derivatives, and arehydrogenated liquid C₅–C₁₂ derivatives, since a mineral oil consists ofparaffins, naphthenes, aromatics and polyaromatics. As described above,the paraffins are n-alkanes or branched alkanes. The naphthenicstructure is actually that of a cycloalkane having at least one ring of6 carbon atoms (or even 5 or 7). Finally, in aromatic derivatives adistinction is made between aromatics and polyaromatics. A distinctionis generally made between two types of crude oils: naphthenic oils andaromatic oils. The product NYFLEX 820 from NYNAS is a typical example ofa naphthenic oil. It has a proportion of 16% of aromatics.

-   -   3) Heavy and light fuels, and more particularly kerosene,        diesel, etc. This family of products is more particularly        preferred.    -   4) Alkylbenzenes, such as decylbenzenes, dodecyl benzenes.    -   5) Esters which are, for example, products of reacting        polyhydric alcohols, such as pentaerythritol, with monobasic        carboxylic acids, such as n-heptanoic acid; alkyl phthalates,        such as diethyl and dibutyl phthalate.    -   6) Alkylpolyaromatic compounds, such as: the mixture of isomers        of dibenzyltoluene (DBT), monoisopropylbiphenyl (MIPB),        phenylxylylethanes (PXE); mixtures of benzyltoluenes and        dibenzyltoluenes, such as those described particularly in        European Patent No. 136230-B1; mixtures of mono- and        bis(methylbenzyl)xylenes, such as those described in European        Patent Application No. 0500345; mixtures of benzyltoluene and of        diphenylethane.    -   7) Vegetable oils, such as rapeseed oils and maize oils, and        also combinations of at least two of the abovementioned        insulating liquids.

The chemically inert organic filler used preferably comprises naphthenicoils or n-paraffins or a mixture of n-paraffins, or comprises fuels.Fuels are more particularly preferred, and even more preference is givento aviation fuels, such as kerosene.

According to the present invention, the polyisocyanate used may bechosen among aromatic, aliphatic and cycloaliphatic polyisocyanates andthose whose molecule contains an isocyanurate ring, having at least twoisocyanate functions in their molecule, and susceptible to reaction withthe hydroxyl functions of a polyol to form a three-dimensionalpolyurethane network, bringing about the crosslinking of thecomposition.

By way of illustration of aromatic polyisocyanates which may be usedaccording to the present invention, mention is made of diphenylmethane4,4′-diisocyanate (MDI), polymeric MDIs, and triphenylmethanetriisocyanate.

By way of illustration of an aliphatic polyisocyanate which may be usedaccording to the present invention, mention is made of the biuret ofhexane 1,6-diisocyanate.

By way of illustration of cycloaliphatic polyisocyanates, mention ismade of isophorone diisocyanate (IPDI), cyclohexyl diisocyanate (CHDI),and dicyclohexylmethane 4,4′-diisocyanate.

Use may also be made of a polyisocyanate polymer whose chain contains atleast two units each of which contains at least one isocyanate function.

The polyisocyanate polymer used advantageously comprises the product offormula:

CAS Reg. Number (CHEMICAL ABSTRACTS registry No.): 9016-87-9 known asPMDI.

The amount of polyisocyanate according to the present invention ischosen in such a way that the molar ratio NCO/OH is between 0.5 and 2,preferably from 0.65 to 1.20.

According to the present invention, the polyol is chosen among polydienepolyols, polyester polyols, and polyether polyols, taken separately orin a mixture.

According to the present invention, the polydiene polyol is preferably ahydroxytelechelic oligomer of conjugated dienes and may be obtained byvarious processes, such as free-radical polymerization of conjugateddienes having from 4 to 20 carbon atoms in the presence of apolymerization initiator, such as hydrogen peroxide or an azo compound,such as azobis-2,2-[2-methyl-N-(2-hydroxyethyl)propionamide] or anionicpolymerization of a conjugated diene having from 4 to 20 carbon atoms inthe presence of a catalyst, such as naphthalenedilithium.

According to the present invention, the conjugated diene of thepolydiene polyol is chosen from the group consisting of butadiene,isoprene, chloroprene, 1,3-pentadiene and cyclopentadiene.

The scope of the invention covers the use of hydroxytelechelic oligomersof conjugated dienes epoxidized along the chain, and also ofhydrogenated hydroxytelechelic oligomers of conjugated dienes.

According to the present invention, the polydiene polyols may havenumber-average molecular weights of at most 7 000 and preferably between1 000 and 3 000. They have functionalities of from 1 to 5, preferablyfrom 1.8 to 3, and a dynamic viscosity, measured at 30° C., of not lessthan 600 mPa.s.

By way of illustration of polydiene polyols, mention is made of thehydroxylated polybutadienes marketed by the company ATOFINA with thenames Poly Bd® R 45 HT and Poly Bd® R 20 LM.

According to the present invention, the composition may comprise one ormore low-molecular weight polyols in addition to the polyol(s)mentioned.

A low-molecular weight polyol is a polyol having a molecular weight offrom 50 to 800.

By way of illustration of polyols of this type, mention may be made ofethylene glycol, propylene glycol, diethylene glycol, dipropyleneglycol, polyether polyols, 1,4-butanediol, 1,6-hexanediol,2-ethyl-1,3-hexanediol, N,N-bis(2-hydroxypropyl)aniline,3-methyl-1,5-pentanediol, trimethylolpropane, pentaerythritol, thepropoxylated bisphenol A marketed by the company AKZO with the nameDIANOL 320 and mixtures of at least two abovementioned polyols.

If use is made of a low-molecular weight polyol, the molar ratio NCO/OHhas to be calculated taking into account the hydroxyl functions borne bythe said low-molecular weight polyol.

If use is made of a crosslinking catalyst, this may be chosen from thegroup consisting of tertiary amines, imidazoles and organometalliccompounds.

By way of illustration of tertiary amines, mention may be made of1,4-diazabicyclo[2.2.2]octane (DABCO), andN,N,N′,N″,N″-pentamethyldiethylenetriamine.

By way of illustration of organometallic compounds, mention may be madeof dibutyltin dilaurate, dibutyltin diacetate, and organic derivativesof bismuth.

The crosslinkable composition of the present invention may be obtainedby mixing the various constituents using any means of agitationsufficient to provide good dispersion of the constituents. Thecomponents may be heated, if necessary, to improve homogenization. Thecomposition may comprise one or more additives, such as antioxidants orcorrosion inhibitors.

The crosslinkable composition of the invention has the advantage ofproviding thermal insulation to the pipeline system(s) passing throughthe conduit, by virtue of its low thermal conductivity, and ofpreventing any convection. In addition, taking into account theresistance of the composition of the present invention to hydrostaticpressure, it may very particularly be used for the thermal insulation ofpipeline systems present in a submarine transfer conduit. This isbecause the density of the crosslinkable composition of the inventionmay be adjusted so as to be close to or even lower than that of thewater at the sea bed.

The crosslinkable composition of the invention, which is liquid when itis processed, has very low shrinkage during its crosslinking, and thispermits provision of an interface of good quality between the gel andthe pipeline systems to be jacketed, and complete filling of the spaceswithin the sheath in which the gel is present, with very good adhesionof this gel to the walls of the conduit and of the sheath.

To illustrate the invention, a description is given below of atransverse section of a conduit.

A conduit generally comprises:

-   -   a sheath which is generally made of steel and may be externally        coated with an anticorrosion coating;    -   various pipeline systems conveying the products, optionally a        pipeline system known as a service pipeline system, where these        pipeline systems may have been externally coated with an        anticorrosion coating, and    -   a space filled by the filling material which consists of the        crosslinkable insulating composition of the invention.

The crosslinkable insulating composition may be put in place by anyappropriate means.

In particular, in one embodiment of the invention it is possible for acrosslinkable composition which has been previously prepared and hasfluidity sufficient to permit the complete filling of the sectorcomprising the pipeline(s) to be injected into the said sector. Thecomposition preferably has a viscosity lower than 200 mPa.s at thetemperature of processing, which is not more than 80° C.

The said composition is then allowed to crosslink. The crosslinkedinsulating composition is characterized by thermal conductivity γ(lambda) lower than 0.25 W/m.k.

The setting time, which is the time necessary for the compositionaccording to the present invention to be completely crosslinked, mayvary within a wide range.

However, this setting time has to be adjusted in such a way that thecomposition according to the present invention can completely fill the(submarine) conduit and can completely satisfactorily wet the pipelinesystem(s) inside the said conduit to provide their insulation.

The person skilled in the art will therefore adjust the proportions ofthe constituents of the said composition and, optionally, the amounts ofcrosslinking catalyst are to be used to obtain a suitable setting time.

The composition of the present invention may also be used for completingthe thermal insulation of pipelines where there is already a primarycoating of insulation.

Secondly, the present invention provides a submarine product-transferconduit comprising at least one pipeline system, optionally at least onepipeline system known as a service pipeline system, one protectivetubular sheath through which the said pipeline systems pass and afilling made of a thermally insulating material physically characterizedin that the thermally insulating material consists of an insulatingcomposition in the form of a gel obtained from a crosslinkablecomposition as defined for the use according to the present invention.

Thirdly, the present invention provides a district heating conduitcomprising at least one PVC pipeline system, transporting hot water fromthe thermal power station to the housing, a tubular protective sheathmade of plastic, PVC or polyethylene, through which the said pipelinesystems pass, and a filling made of a thermally insulating material,physically characterized in that the thermally insulating materialconsists of an insulating composition in the form of a polyurethaneelastomer gel as defined for the use according to the present invention.

Fourthly, the present invention provides a process for thermalinsulation of a conduit for transporting liquid materials, obtained froma crosslinkable insulating composition as defined for the use accordingto the present invention, the said process comprising the followingsteps:

-   -   a) Intimate mixing of the polyol component and of the insulating        liquid filler component of the said insulating composition,    -   b) Addition, to the mixture of step a), of the polyisocyanate        component of the said insulating composition, with intimate        mixing of all of the components,    -   c) Casting or injection moulding of the resultant mixture from        step b) into the interstitial space formed between the outer        surface of the conduit and the inner surface of the protective        sheath,    -   d) Crosslinking and solidification in situ to obtain the        thermally insulated conduit ready for use at its point of use.

One version of this process consists in implementing steps c) and d) ina mould to obtain premoulded sections of thermal insulation for amaterials-transport conduit, with assembly around the conduit.

Finally, the present invention provides premoulded sections of thermalinsulation for a conduit which have been obtained according to the saidversion of the process, prior to assembly around the conduit.

Below we give some illustrative embodiments of crosslinkablecompositions which may be used according to the present invention.

The compositions were prepared using the following constituents:

-   -   Poly Bd® 45 HT (termed Poly Bd® below): hydroxylated        polybutadiene of number-average molar mass Mn of 2 800        (determined by steric exclusion chromatography) with a hydroxyl        index I_(OH) expressed in milliequivalents per gram of resin        (meq/g) of 0.83, viscosity of 5 000 mpa.s at 30° C. and density        of 0.90.    -   A mixture of n-paraffins, the main component being n-octadecane        (LINPAR 18–20 from CONDEA).    -   A naphthenic resin, Nyflex 820 grade, produced and marketed by        NYNAS.    -   A prepolymer such as UREFLEX MU 55 marketed by Baulé.    -   Isonate M 143 (termed Isonate below) marketed by the company DOW        CHEMICAL: polymeric MDI having an NCO content of 29.16%,        functionality of 2.2 and viscosity of 130 mPa.s at 20° C.    -   Dibutyltin dilaurate (crosslinking catalyst) termed DBTL below        (FASCAT 4220CL).    -   “No Air” liquid antifoam marketed with this name by the company        BARLOCHER.

EXAMPLES

The following examples illustrate the invention without limiting itsscope.

1. Formulations:

Some examples of formulations prepared are given in the following table:

Compo- Compo- Compo- Compo- Compo- sition sition sition sition sition 12 3 4 5 Poly Bd R 45 HT 100 100 100 100 100 N-paraffin mixture with 250n-octadeoane >60% LINPAR from CONDEA Kerosene (Kedrul 212 200 200 500from TOTALFINAELF) NYFLEX 820 — 200 FASCAT 4220 CL 0.1 0.025 0.1 0.1 0.1(Dibutyltin dilaurate) “No Air” liquid — 0.5 0.5 0.5 0.5 Isonate N 14312.7 — 12.7 12.7 % NCO = 29.16 Ureflex MU 55 47.04 47.04 % NCO = 5.25NCO/OH 1.05 0.7 0.7 1.05 1.05Method:Composition 1:

The mixture Poly Bd R 45 HT/LINPAR 18–20 paraffin is degassed at 80° C.for 1 hour under vacuum. The mixture is then cooled to 50° C. foraddition of the isocyanate Isonate M 143 and then left to crosslink at50° C.

Composition 2:

The mixture Poly Bd R 45 HT/NYFLEX 820 is degassed for 1 hour undervacuum at ambient temperature. The polyisocyanate prepolymer is thenadded and the crosslinking takes place at ambient temperature.

Compositions 3–5:

Poly Bd R 45 HT and kerosene are mixed with stirring at ambienttemperature. The polyisocyanate prepolymer is then added and thecrosslinking takes place at ambient temperature.

2. Thermal conductivity measurements:

The tests were carried out on FOX series 300 (DELTA) or SOFT-K thermalconductivity measurement equipment conforming to ASTM C518 and ISO 2581.The measurements were made on specimens of size 30×30×2 cm placedbetween the upper segment (cold plate) and the lower plate (hot plate)of the equipment.

The results are given in the following table:

Cold plate/ Compo- Compo- Compo- Compo- Compo- hotplate sition sitionsition sition sition Temp. ° C. 1 2 3 4 5 Lambda 0° C./20° C. 0.12760.136 0.139 0.125 at 10° C. W/m.k. Lambda 10° C./ 0.1385 0.115 0.1350.128 at 25° C. 40° C. W/m.k.3. Conclusion:

The values obtained for thermal conductivity demonstrate theeffectiveness of the crosslinkable compositions of the invention inthermal insulation.

1. District heating conduit comprising at least one PVC pipeline systemtransporting hot water from a thermal power station to a housing, atubular protective sheath made of a plastic, PVC or polyethylene throughwhich the said PVC pipeline system passes, and a filling made of athermally insulating material, wherein the thermally insulating materialconsists of an insulating composition in the form of a polyurethaneelastomer gel composition prepared by reacting a crosslinkablecomposition comprising at least one polyol and at least onepolyisocyanate in the presence of at least one liquid organic fillerchemically inert to the polyisocyanates.
 2. Process for thermalinsulation of a conduit for transporting materials, the conduit havingan outer surface and a protective sheath, the protective sheath havingan inner surface, an interstitial space between the outer surface of theconduit and the inner surface of the protective sheath comprising a)intimately mixing of at least one polyol component and at least oneinsulating inert liquid organic filler component chemically inert topolyisocyanates b) adding to the mixture of step a) at least onepolyisocyanate component with intimate mixing of all of the components,c) casting or injection moulding of the resultant mixture from step b)into the interstitial space and d) crosslinking and solidification insitu to obtain the thermally insulated conduit ready for use at itspoint of use.
 3. Process according to claim 2 in which the steps c)moulding and d) crosslinking are implemented in a mould to obtainpremoulded sections of thermal insulation for the conduit fortransporting liquid materials, and comprising an additional step e)assembling these premoulded sections around the conduit.
 4. Premoldedsections of thermal insulation for a conduit which have been obtained bythe process of claim
 2. 5. The method according to claim 2, wherein thesaid organic filler is kerosene.
 6. Conduit for sub-marine producttransfer, comprising at least one pipeline system, optionally at leastone pipeline system known as a service pipeline system, having aprotective tubular sheath through which the said pipeline system passesand a filling made of a thermally insulating material, wherein thethermally insulating material consists of an insulating composition inthe form of a gel obtained from a crosslinkable composition comprisingat least one polyol and at least one polyisocyanate in the presence ofat least one liquid organic filler chemically inert to thepolyisocyanates.
 7. The process according to claim 2, wherein the inertliquid organic filler is more than 20% by weight of the entirecomposition.
 8. The process according to claim 2, wherein the inertliquid organic filler represents from 50 to 95% by weight of the entirecomposition.
 9. The process according to claim 2, wherein the inertliquid organic filler is selected from the group consisting of C₁₈–C₂₀n- or iso-paraffins, chlorinated paraffins; heavy or light fuels; C₅–C₁₂naphthenic oils or resins; aromatic compounds and polyaromaticcompounds, optionally containing one or more heteroatoms.
 10. Theprocess according to claim 2, wherein the inert liquid organic filler isan n-paraffin or a mixture of n-paraffins.
 11. The process according toclaim 2, wherein the inert liquid organic filler is a naphthenic resin.12. The process according to claim 2, wherein the inert liquid organicfiller is an aviation fuel.
 13. The process according to claim 2,wherein the polyol is selected from the group consisting of polyesterpolyols, polyether polyols and polydiene polyols.
 14. The processaccording to claim 2, wherein the inert liquid organic filler is anoptionally substituted aromatic or polyaromatic compound, optionallycontaining one or more heteroatoms.
 15. The process according to claim2, wherein at least one polyol is polydiene polyol having anumber-average molecular weight of no greater than 7 000, and afunctionality of from 1 to
 5. 16. The process according to claim 15,wherein the polydiene polyol has a number-average molecular weight ofabout 1000 to
 3000. 17. The process according to claim 15, wherein thepolydiene polyol is a hydroxytelechelic oligomer of a conjugated diene.18. The process according to claim 15, wherein the polyol has anumber-average molecular weight of about 1000 to
 3000. 19. The processaccording to claim 15, wherein the polydiene polyol is ahydroxytelechelic oligomer of butadiene.
 20. The Process according toclaim 2, wherein the polyisocyanate is an aromatic, cycloaliphatic, or aprepolymer.
 21. The process according to claim 2, wherein thepolyisocyanate is diphenylmethane 4,4′-diisocyanate (MDI) or a polymericMDI.
 22. The process according to claim 2, wherein the polyisocyanate isa prepolymer prepared from a hydroxytelechelic oligomer of a conjugateddiene, polyol and a polyisocyanate.
 23. The process according to claim2, wherein the polyol comprises one or mare low-molecular weightpolyols.
 24. The process according to claim 23, wherein thelow-molecular weight polyol(s) has (have) a molecular weight of from 50to
 800. 25. The process according to claim 2, wherein the NCO/OH molarratio is between 0.5 and
 2. 26. The process according to claim 2,wherein the NCO/OH ratio is between 0.65 and 1.20.
 27. The processaccording to claim 2, comprising adding a crosslinking catalyst to themixture.
 28. The process according to claim 27, wherein the saidcrosslinking catalyst is dibutyltin dilaurate.
 29. The process accordingto claim 2, the insulation having, after crosslinking, a thermalinsulation factor below 0.25 W/m.k.